1. Field of the Invention
The present invention relates to a device for which a quantum effect is utilized, and a method of producing the same.
2. Description of the Related Art
Owing to the recent progress of the semiconductor technique, high integration of devices and miniaturization of device size have been progressing. Due to the miniaturization, it is necessary to develop a new device which has a structure different from that of the conventional transistor. For such a new device, a device for which a quantum effect is utilized has been studied (see THE JOURNAL OF THE INSTITUTE OF ELECTRONICS, INFORMATION AND COMMUNICATION ENGINEERS, Vol. 72, No. 12, pp. 1387-1391, December 1989).
In order to cause the quantum effect, developments of a technique for forming dots or strip wires each having a size of the order of an electron wavelength, and a technique for constituting a circuit by coupling the dots and the strip wires are required.
For a quantum device whose operation is based on the quantum effect, various devices are now being developed. Especially, a device for controlling the electron transfer by utilizing the resonant tunneling effect has been developed. The quantum device for which the resonant tunneling effect is utilized includes a minute conductor region in which the energy states which can be taken by electrons are quantized, and a pair of conductor regions (electrodes) adjacent to the minute conductor region via a thin barrier film through which electrons can tunnel. Such a quantum device is disclosed, for example, in U.S. Pat. No. 4,912,531 (Reed et al.).
In order to realize the above quantum device, a technique for forming a microstructure with good reproducibility is required. A conventional quantum device is produced by laminating a plurality of different kinds of thin compound semiconductor films on a semiconductor substrate. As a result, in the quantum device, electrons move freely in a direction parallel to the main plane of the substrate, and electrons are confined in the quantized region in another direction perpendicular to the main plane of the substrate.
However, in the above prior art, it is difficult to form a region which has a very small thickness which is measured along a direction parallel to the main plane of the substrate.